The present invention is directed to mass transfer devices and, more particularly, to vapor-liquid contact trays and methods of assembling such trays.
Trays, such as counter-flow trays and cross-flow trays, are commonly used in mass transfer columns to promote contact and mass transfer between ascending and downwardly flowing fluid streams. The ascending fluid is typically vapor and the descending fluid is typically liquid, although liquid-liquid and vapor-vapor systems are also known. Each tray normally extends horizontally across substantially the entire horizontal cross section of the column and is supported around its perimeter by a ring welded to the inner surface of the circular column wall or shell. Various trusses or beams are also used to provide intermediate support for the tray.
It Vapor-liquid contact trays of the type described above contain one or more downcomers that are positioned at openings in the tray to provide passageways for liquid to descend from one tray to an adjacent lower tray. Prior to entering the downcomer, the liquid travels along the tray upper surface and interacts with ascending vapor that passes through valves or other openings provided in selected portions of the tray deck. That portion of the tray deck containing vapor openings is commonly referred to as the xe2x80x9cactive areaxe2x80x9d because of the vapor and liquid mixing and frothing that occurs above the tray. In order to increase the vapor handling capacity and mass transfer efficiency of the tray, it is generally desirable to maximize the active area of the tray by providing vapor openings in as much of the tray deck as possible.
In order to facilitate installation and removal of the above described trays within a column, the trays are typically fabricated in smaller pieces or panels that are sized to fit through openings or manways in the column shell. Once the tray panels are carried through the manways, they are placed on the support beams with the edges of each tray panel overlapping the edges of adjacent tray panels. The tray panels are then typically bolted together along their overlapped edges to resist against lifting or separation of individual tray panels, either by the upward force that is exerted by the ascending vapor stream, or by the vibrations that can occur during operation of the column.
Bolting the multiple tray panels together for each of the numerous trays typically found in a mass transfer column is an extremely labor intensive and time consuming process. In order to reduce the assembly time, a hinged joint has been previously developed to join together adjacent tray panels without requiring the use of bolts. This hinged joint is formed by constructing spaced apart tabs that extend outwardly along the edge of one tray panel and complementally sized and positioned slots spaced a preselected distance from the edge of an adjacent tray panel. The tabs are then inserted into the slots by slightly elevating the opposite end of one of the tray panels, sliding the tabs into the slots, and then lowering the raised end of the tray panel to a horizontal position.
While the hinged joint described above allows for more rapid assembly of tray panels, it does not lock the tray panels together and they may become separated as a result of operational vibrations within the column or if the tray should bow upwardly under the force of high vapor flow rates. In order to resist against separation of the tray panels under anticipated vapor flow rates, the tabs must be of sufficient length so that they do not slip out of the slots when the tray panels bow upward. These longer tabs, however, may overlap and impede the flow of vapor through any vapor openings or valves that are provided near the hinged joint. As a result, the tabs reduce the active area available on the tray deck for vapor and liquid interaction. Another disadvantage of the conventional hinged joint is the overlapped portions of the tray panels are elevated above the surrounding portions of the tray by the thickness of one tray panel. This elevated portion of the tray forms a hump that can disrupt the desired liquid flow pattern along the upper surface of the tray deck and can interfere with the placement of weirs or other structural components on the tray deck.
A need has thus developed for a way to quickly join together adjacent tray panels in a manner that reduces the risk of inadvertent separation during use or installation, does not impede the desired liquid flow pattern on the tray surface, and allows the vapor openings to be positioned more closely to the joint.
In one aspect, the present invention is directed to a vapor-liquid contact tray having a plurality of individual planar tray panels that are joined together to form a tray deck having a planar upper surface. Liquid streams flow along the upper surface of the tray panels and interact with vapor ascending through valves provided in the tray panels. At least two of the tray panels are releaseably joined together by a hinged joint formed along overlapping edge portions of the tray panels. The hinged joint is formed in part by fingers that extend outwardly from one tray panel and are received within slots located in the adjacent tray panel. The fingers have a distal segment and a proximal or attached segment and a first offset bend formed therebetween so that the distal segment is located in a plane underlying the attached segment. A second offset bend is formed in the adjacent tray panel near the overlapped edge portion and places the overlapped edge portion in a plane underlying the main body of the tray panel. The finger receiving slots are located in the second offset bend and are positioned so that the fingers extend through the slots and engage an undersurface of the adjacent tray panel. The hinged joint also includes a locking mechanism comprising at least one downturned locking flange formed in the overlapping edge portion of the one tray panel and extending downward into an opening in the overlapped edge portion of the adjacent tray panel. The hinged joint allows the tray panels to be quickly and easily assembled, with the locking mechanism securing the tray panels against inadvertent horizontal separation during operation of the column. The presence of the locking mechanism allows the fingers to be of a length sufficient to provide vertical support for the adjacent tray panel without the need for additional length to resist lateral separation. As a result, the vapor flow valves or openings can be placed close to the hinged joint to increase the tray active area without interference by the fingers blocking vapor entry into the valves. Advantageously, the construction of the hinged joint allows the overlapped margins of the tray panels to be positioned at or below the top surface of the main bodies of the trays so that disruptions in the flow of liquid across the top surface of the trays are not experienced. The planar hinged joint also facilitates placement of weirs or other structural components on the tray because notches or bends need not be formed in the structural components as is required by the presence of a hump in conventional hinged joints.
In another aspect, the invention is directed to method of assembling tray panels using the hinged joint described above.